comparing bearing and gear options: how to buy bearings based on life, not just price

• What is the #1 failure component in rotating equipment?• Do you trust your bearings?• Do you trust you bearing provider?• Did the life your bearing provider told you actually happen?• Do they tell you that they make perfect bearings and the reason

their bearings did not last is that you destroy them in your assets?• Are you able to test bearings in your asset, product or design with

the real loading conditions unique to every fielded asset?• What is the effect of different oil and additives on your bearings?• Have you considered Chinese or Indian bearings but were afraid of

quality or counterfeit?• Does bearing performance anxiety keep you up at night? Look at

the clock - do you know how your fielded bearings are degrading right now and what that will that cost tomorrow, next month and for the next 20 years?

Why Focus on Bearings?

05/01/2023How to Buy on Life, Not Just Price

1. How many of my bearings need to be replaced but what cost, life and size this year and over the next 10-20?

2. Can I negotiate a win-win long term supply contract and warranty based on my newly gained knowledge on life?

3. How are bearings of the same part number different between vendors and assets?

4. How much more should I pay my vendor to to provide 2X life?

5. Should I use my current supplier of lubricant and additives or should that be customized mix to the specific needs of a particular asset, location and duty cycle?

The Demand for Better Bearings is Forcing OEMS & Operators to ask Themselves Many Tough Questions

Which Require Bearing Comparisons


DigitalClone Live UI

Site 1

Site 2

Site 3

Site 4

Site 5

Site 6

Site 7

Site 8

Fleet 1


GBX Subcomponent Assessment

Note: Clipper GBX Example


Gearbox Bearing Performance Comparison


“As Is”

Quantify Impact of: Lubrication change, auto-lubrication systems, uptower change, etc.

Prognostics allows you to quantify “what-if” scenarios to extend RUL.

“To Be”Years Until Gearbox FailureYears Until Gearbox Failure

How to Buy on Life, Not Just Price

GE 1.5MW GEARBOX

Trade-Off Studies Asset/Customer specific trade-off option to confidently predict impact on life/ROI (e.g. gearbox replacements)

ROI Optimization All trade-offs based on ROI at the individual asset level/group, maximizing ROI for the fleet.

Gearbox Bearing Configuration Option

May 1, 2023

OEM ConfigurationGearbox w/ OEM 1Gearbox w/ OEM 2Gearbox w/ OEM 3

1. The conventional approach to bearing selection is based solely on bearing engineer experience with limited test data, which can lead to unexpected performance in the field

2. The same bearing model from different vendors will behave differently in the field. Sentient provides the ability to understand life and performance of bearings from multiple vendors, with different lubricants and additives in your specific asset or system, without physical testing

3. Sentient's computational modeling approach provides the ability to "virtually test" the effect of operation and maintenance (O&M) changes, and determine an optimum O&M strategy for life extension and asset management

3 Key Points


Challenge of Machinery OEMs in Bearing Selection


Selecting bearings that meet design specifications while balancing performance and cost

Standard selection criteria include• Dimensional constraints: inner bore, outer bore, and width• Tolerance: dimensional accuracy and operating tolerances• Rigidity: Elastic deformation occurs along the contact surfaces of a

bearing’s rolling elements and raceway surfaces• Load capacity

Conventional Approach to Life Rating


Static load rating, C, is defined as the static load which the bearing can carry for 1,000,000 revolutions with 10% probability of fatigue failure

Bearing life, in millions of revolutions with 10% probability of fatigue failure:

p

PCL

10

P = equivalent bearing load, kNp = 3 for ball bearings 10/3 for roller bearings

Empirical Adjustments to Life Ratings


Adjustments are made to life ratings based upon materials and operating conditions

aM = Adjustment for material - Factor of 1.0 for vacuum-degassed steels - Factor for premium steels is 0.6-1.0

aL = Adjustment for lubrication conditions - Determined by lubricant film parameter, Λ = h/Rq

Limitations of Conventional Approach


Lack of accounting of varying operating conditions• Operating temperature• Misalignment

Lack of accounting of internal features• Surface finish (roughness, skewness, kurtosis)• Surface coatings• Roller crowning

Lack of accounting of material characteristics• Grain size distribution• Presence of inclusions and defects• Residual stress distribution

100X - Case-Core Transition

Parameter Conventional Sentient DigitalCloneVarying Load Yes YesVarying Speed No YesLubricant No YesSurface Finish No YesMicrogeometry No YesMaterial Quality No Yes

Sentient vs. Conventional Approach


Sentient’s Technical Approach


Tribological Analysis and Failure Prediction

Material and Surface Characterization

Component-Level Analysis

System-Level Analysis






-700

-600

-500

-400

-300

-200

-100

0

100

200

0 50 100 150

Resid

ual S

tres

s, M

Pa

Subsurface Depth, µm

Residual StressMaterial Quality

Surface Roughness

100X

Non-metallic Inclusion


Subsurface Crack Network

Interfacial Contact Pressure and Subsurface Stress







05/01/2023

All Bearings are NOT Created Equal…


Bearing material microstructure, surface finish, and material quality impact life…depending upon location and stresses experienced

Here’s how some of these factors can influence life for a wind turbine gearbox bearing

Stress / Life Curve

Bearing Supplier

Hardness (Ra) Range 0 to 4500 um

depth

Microstructure Inclusions

Microstructure Quality

Supplier 1 60–58 HRC

Supplier 2

60-53 HRC (Design

requirement >58 HRC)

Digi

talC

lone

® S

imul

atio

n

HSS Bearing DigitalClone Comparison

BEST BEST BEST

Stress / Life Curve

Cycles to Damage (L66)

Max

Con

tact

Pre

ssur

e (M

Pa)

Stress – Life Curve

Supplier 2

Better LifeBett

er S

tres

s Pe

rfor

man

ce

Outer Race

Inner Race

BEST

Oute

r Rac

e

Inner Race

Supplier 1

New Prognostic Solution to Predict Failures• Prognostics vs. Diagnostics • Data Model versus Material Science Model - Compatible

• Calculates Remaining Useful Life (RUL) and Recommends Options to Extend Life.

• Simulates “what if” scenarios to optimize performance.

• Enables efficient Asset Management.

• Reduces the Time and Cost of Physical Design Testing

How to Buy on Life, Not Just Price 05/01/2023

Bearing Selection: Model Designators


Cylindrical roller bearingLips on outer ringWidth series 0Diameter series 370 mm bore (14x5)

NU2 14

3

Bearing models have standard designators that are universal to all major manufacturers

[code for bearing type][code for bearing cross section][code for bore size]

Case Study: Tapered Roller Bearings in Industrial Application


FEA Analysis

0

500

1000

1500

2000

2500

3000

3500

IR OR IR OR

DB_Inboard DB_Outboard

Equivalent Crown Radius

KOYO NTN TIMKEN

Microgeometry Measurements

Supplier A Supplier B Supplier C

Equi

vale

nt C

rown

Rad

ius (

mm

)

Bearing-Shaft Assembly

Material Model Development

• Industrial bearing was used for microstructure residual stress, chemical and micro-hardness analysis

• Optical zoom microscopy, scanning electron microscopy (SEM), Inverted microscopy, optical profilometry, and micro-hardness testing are used for characterization

• Goal is to identify key microstructural features, input to DigitalClone fatigue damage simulation, based on ASM standards


As-Received EDM Sectione

d

Supplier A Supplier B Supplier CSurface Roughness Measurement


Supplier A

Metallic Inclusion

Supplier B

Material Quality Measurement


Supplier C

Non-metallic Inclusions

Non-metallic Inclusions


40

45

50

55

60

65

0 500 1000 1500 2000

Rock

wel

l Har

dnes

s

Subsurface Depth (µm)

Supplier ASupplier BSupplier C

-1000

-800

-600

-400

-200

0

200

0 20 40 60 80 100 120 140 160 180 200

Resi

dual

Str

ess (

MPa

)

Subsurface Depth (µm)

Supplier ASupplier BSupplier C

Subsurface Hardness and Residual Stress


Deterministic Mixed-EHL

Physics-based modeling of interfacial surface contact, frictional heating, and lubrication

Contact Pressure

Asperity Contacts

Lubricant Pressurizatio

n

Surface Deflection

Piezoviscosity

Asperity Contact

Subsurface Crack Pattern


Supplier A

Supplier B

Supplier C

Contact Surface

Contact Surface

Contact Surface

Operating Condition 1: Low Gear, Left MisalignmentDigitalClone Prediction of Bearing Life

Supplier A

Supplier C

Supplier B


Supplier A

Supplier B

Supplier C

DigitalClone Prediction of Bearing LifeOperating Condition 2: High Gear, Right Misalignment


1. The conventional approach to bearing selection is based solely on bearing engineer experience with limited test data, which can lead to unexpected performance in the field

2. The same bearing model from different vendors will behave differently in the field. Sentient provides the ability to understand life and performance of bearings from multiple vendors, with different lubricants and additives in your specific asset or system, without physical testing

3. Sentient's computational modeling approach provides the ability to "virtually test" the effect of operation and maintenance (O&M) changes, and determine an optimum O&M strategy for life extension and asset management

3 Key Points


comparing bearing and gear options: how to buy bearings based on life, not just price

Technology